Re: [Discuss-gnuradio] How do I know when my flow graph has finished in a non-blocking way?

Hi Eskil,

QT has its own threading library that you'll need to use to spawn a new thread to do the blocking calls in:
http://pyqt.sourceforge.net/Docs/PyQt4/qthread.html (sadly, that page is still C++ centric)

PyQT4 usually comes with a set of nice examples, which have been useful for me over the last days; for me, those installed to
/usr/share/doc/PyQt4-devel-4.10.1/examples
and for your threading intents, you might want to look at
/usr/share/doc/PyQt4-devel-4.10.1/examples/network/threadedfortuneserver.py

Greetings, and happy hacking,
Marcus

On 02.07.2014 20:27, Eskil Varenius wrote:

Dear friends of GNU Radio,  I have a question about blocking, threads and GUI. Thing is, I am writing  an GUI application (in PyQT4) where the user can start a GNU Radio  flowgraph by a button. The flowgraph records data from an USRP and some  additional blocks. Now, I want only a finite amount of data so I have added  a "head" block to my flowgraph. The obvious way to run this is as the  following pseudo code program:  # Define flowgraph  class USRP(gr.top_block)  ...connect USRP -> head_block_> file_sink  # Define GUI  GUI__init__()      gui.button.clicked.connect(startUSRP) ...  # Define action to be taken when button clicked, i.e. start flowgraph  startUSRP()    tb=USRP()    tb.start()    tb.wait() # Will block everything until finished  #  define and run GUI  main()      app = QtGui.QApplication(sys.argv)      window = main_window()      window.show()      sys.exit(app.exec_())  if __name__ == '__main__':      main()    My code runs as expected, in the sense data is produced, but tb.wait is a  blocking call. This means that my GUI will freeze until the flowgraph has  ended. The GUI must not be blocked during flowgraph execution. Also, I  would like to track the progress of the flowgraph (the number of elements  processed / total elements requested). I tried to search online, and there  is some related information, but unfortunately I have not managed to  understand how to put the pieces together yet. I imagine something like  using QTimer to periodically check the status of the flowgraph, by asking  the flowgraph in some way.  This flowgraph ends with writing to a file, after the head_block. Hence, I  suspect that just checking the head_block might not give me all data?  Either I need to add a small extra delay to make sure the file sink gets  all data, or check the number of items passed to the file sink itself? So I  guess the short question is:  How to periodically check if a started flowgraph has finished, without  using a blocking call such as tb.wait?    I would be very grateful for any hints. I don't know much about C++ and  threading, which makes finding clues from the C++ API more difficult.  However, I am eager to learn if anyone would enlighten me on this.    Best regards,  Eskil    

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